Self flocculating separation medium and method

ABSTRACT

Disclosed is a combined flocculating and clarifying medium for flocculating and separating solid particles from waste water comprising a mixture of solid filtering or aggregating particles and a dry flocculating agent effective to flocculate the solid particles to form larger and heavier aggregates with the filtering or aggregating particles in the waste water and filtering or gravity separating the formed aggregate from the waste water. Preferably, the filtering and aggregating particles are silicious particles, such as rice hull ash, diatomaceous earth, and perlite. The flocculating and clarifying medium can be combustible or can chemically fix the aggregated solid particles in a silicious cement, which solid particles can include heavy metal particles in silicious cement.

This application is a division of application Ser. No. 08/390,627 filedFeb. 17, 1995, now U.S. Pat. No. 5,637,229.

FIELD OF THE INVENTION

The present invention relates to separation mediums, such as gravityseparators and filter aids for and methods of separating or filteringsolids from waste water.

BACKGROUND OF THE INVENTION

Large quantities of liquids containing unfiltered solid particles, suchas liquid waste, in the past have been discharged in the environmentwithout filtration separation. Current federal and state regulationslimit the discharge of such liquids and liquid wastes into theenvironment. U.S. Pat. No. 4,465,605 is directed to filtration of solidsfrom waste with biogenetic silica, such as rice hull ash, which providesgood filtration. U.S. Pat. No. 5,362,407 is directed to gravityclarifiers or separators for gravity separating solid particles inliquids, such as oil or oil and water.

Waste waters containing large quantities of hazardous metals have beendischarged in the environment without treatment. Current federal andstate regulations limit the hazardous metal concentrations in wastewater and are extremely severe and are frequently based on analyticaldetection limits. Most metals are present in the waste waterconcentrations which can range from 10 to 4000 parts per million. Undersome current regulations, all hazardous metal concentrations in wastewater are required to be less than 300 parts per million and some toless than 1 part per billion. The hazardous materials include cadmium,chromium, copper, lead, manganese, selenium, as well as others. Inaddition, it is desirable to remove and sequester into the removedsolids (filter cake) all metals, some of which are currently consideredto be nonhazardous, such as zinc. U.S. Pat. Nos. 5,106,510 and 5,207,910are directed to combined filtration and fixation of heavy metals.

European patent application (PCT) published on Dec. 29, 1993 underPublication No. 0575329 is directed to a filter aid or medium and amethod of filtering liquid wastes which have good filtration, good flowrates through the filter cake, and have a heat value of the resultingfilter cake containing the filtered solids of at least 5000 Btu perpound of filter aid; and this qualifies as a fuel for industrialboilers, furnaces, and kilns. Combustible filtering particles, such asrubber particles, in a size effective to filter the particles, alone orwith up to about 70 percent silicious filtering particles, are setforth.

Coagulation/flocculation agents are utilized in water filtration andclarification applications. Coagulation and flocculation are essentiallyan electro-physical phenomena where particles of like electrostaticcharge are pulled together using an agent with the opposite charge.Thus, the charged contaminated particle and the flocculating agent drawtogether and combine to make a larger and heavier particle or aggregate.Since larger and heavier particles are generally the easiest to settleout of and separate from waste water, such as by gravity separation orby filtering, this separate flocculation technology is common in watertreatment.

Both natural and synthetic coagulation/flocculation agents have beenused. Commonly used synthetic flocculating agents are organic based highmolecular weight polyacrylamides, polyamines, amine quaternary ammoniumand others. These polymers are soluble in water and can be manufacturedwith specifically designed charge polarity and magnitude. Polymers arecommonly sold in dry, emulsion, and liquid form. Polymeric watertreatment flocculation chemicals are a huge commercial industry withmany large and small companies involved in the manufacture and sales ofthe product. Among natural coagulation/flocculation agents are naturalclay type polymers from Cetco (a division of American Colloid), Biomin,and Southern Clay, natural alums, iron, sulfates, ferric chloride,calcium chloride and swelling clays. These coagulation/flocculationagents can be cationic, anionic, or nonionic and are added separately tothe waste water to be filtered or cleared.

Coagulation/flocculation agents when added to waste water separately orby themselves are difficult to use because of their complicated andtroublesome material handling characteristics. In dry form, syntheticpolymers have to be diluted twice prior to use. The first dilution iscritical because the particles have to be individually wetted or theywill flock themselves prior to complete dispersion making an ineffectivemess. There is no recovery from this development; and when it occurs,the mess must be discarded, which is a problem in and of itself, and theprocess started again.

Liquid and emulsion polymers largely solve this problem, but theygenerate problems of their own. They dramatically raise the costs ofusing organic polymers. Also, the liquid and emulsion products cannot bemade as concentrated dry products so more pounds of liquid/emulsionpolymers are required for a reaction equivalent to the former.

In both cases polymer solutions are extremely slippery, sticky, andtenacious materials that create serious safety hazards if spilled. Whenoverdosed, they tend to create undesirable consequences involving thecontaminant particles, that are stringy, clumpy floccs in waste waterequipment. If extremely overdosed, the excess polymer gets ontoapparatus surfaces which creates problems especially if the excess getsinto filter screens and cloths which it clogs thus interrupting thefiltration operation.

Although polymer flocculation is quite effective at massing smallerparticles into larger, more manageable, or filterable particles, thereare additional problems. Polymer formed floccs are gelatinous,deformable globs that are quite delicate to handle. If over agitated,the floccs degrade to smaller particles that are difficult to remove.Even in their largest form they are deformable which makes themdifficult to filter. Thus, flocculation makes large aggregates that areeasier to filter but makes deformable aggregates that are difficult tofilter.

In addition, in many waste water treatment operations, polymers are onlyone of the chemicals added. Precipitants, oxidizers, and other agentsare often included in the treatment protocol. In a great many occasions,filter aids are also required to defeat the problems created by thedeformable nature of the floccs.

It would be highly desirable to provide a combined flocculating andclarifying medium which has the advantages of flocculation andcoagulation of smaller particles into larger aggregates which do notdeform under the conditions of use, such as in filtering, and add weightso that they readily settle or sink in the waste water in gravityseparation, and methods of separating solids from waste waters, such asby gravity or filtering which avoids problems involved with the separateapplication of coagulant/flocculating agents to waste waters in removingsolids from them.

SUMMARY OF THE INVENTION

The present invention is directed to a combined flocculating andclarifying medium for and methods of separation of solids from wastewaters, such as by filtering or gravity clarification by which the aboveadvantages are obtained, the problems of separate introduction ofcoagulation/flocculation agents are avoided, and by which good settlingcharacteristics and filtration characteristics with good flow rates areobtained.

The foregoing is obtained by combining a dry flocculating agent (eithersynthetic or natural) with solid aggregating particles which providesself flocculating and aggregating particles which perform better thaneither component alone and in which the combination of flocculent agentand clarifying medium solves a number of problems associated withseparately introducing flocculating agents into the waste water to befiltered or cleared. The combined flocculating and clarification mediumof the present invention comprises a mixture of dry flocculating agentand solid aggregating or filtering particles, the dry flocculating agentflocculating the solid particles in the waste water with the aggregatingor filtering particles to form larger and heavier aggregates effectivefor gravity clarification and/or filtration of the flocculated solidaggregates from the waste water.

The flocculating agent can be natural or synthetic or a mixture thereof.A preferred range for most flocculating agents is from about 0.1 percentto about 85 percent by weight of the combined filter aid. Preferably, inutilizing natural flocculating agents, the amount ranges from about 25percent to about 85 percent by weight of the mixture, and when utilizingsynthetic flocculating agents, from about 0.1 percent to about 5 percentby weight of the mixture.

The flocculating agent can be cationic, anionic, or nonionic dependingon the solid particles to be flocculated and filtered or cleared.

The aggregating particles are solid particles, preferably siliciousparticles or silicious particles combined with combustible particles,such as rubber particles, coal fines, petroleum cake, and mixturesthereof. The silicious particles preferably comprise biogenetic silicaparticles, such as rice hull ash and particles from plants that containhigh quantities of silica, such as stalks and hulls of rice, esquisetum(horsetail weeds), certain bamboos and palm leaves, particularlypolymra, pollen, and the like, all of which when burned leave a porousash that is highly desirable as a filtration aid. The siliciousparticles include diatomaceous earth and perlite.

Accordingly, it is an object of the present invention to provide acombined flocculating and clarification medium for separating solidsfrom waste waters which avoids the problems of separate addition ofcoagulation/flocculating agents to the waste waters.

A further object of the present invention is to provide a flocculatingfilter aid which avoids the problems of separate addition ofcoagulation/flocculating agents to waters in filtering solids from them.

A further object of the present invention is to provide a flocculatinggravity separation medium which avoids the problems of separate additionof coagulation/flocculating agents to waters in gravity separation ofsolids from them.

It is a further object of the present invention to provide a method ofseparation or clarification of particles from waste water, such as byfiltration or by gravity separation, which includes flocculation of theparticles with solid aggregating particles into heavier and larger solidaggregates in waste water which has the aforementioned desirableproperties and advantages.

It is a further object of the present invention to provide a combinedflocculating and clarifying medium, such as a filter aid and a gravityseparating medium for flocculating solid particles in waste waters withsolid aggregating particles and filtering or gravity separating theflocculated solid aggregates from waste waters which comprises a mixtureof solid filtering or aggregating particles and a dry flocculating agenteffective to aggregate at least a portion of the solid particles withthe filtering or to aggregate particles in the waste water effective tofilter or gravity separate the flocculated solid aggregates from thewaste water.

It is still a further object of the present invention to provide such aflocculating filter aid in which the resulting filter cake has asufficient heating or Btu content for incineration as a fuel forindustrial boilers, furnaces, and kilns under federal recyclingregulations.

A further object of the present invention is to provide such aflocculating filter medium in which precipitated dissolved metals inwaste waters are flocculated with solid aggregates to form filterparticles, filtered, and chemically fixed in the filter medium, theresulting filter medium being nontoxic and nonhazardous.

Other and further objects, features, and advantages appear throughoutthe specification and claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a combined flocculating andclarification medium, such as a filter aid or gravity separation aid ormedium and methods therefor in which solid particles in waste water, andparticularly small particles, are flocculated by the combinedflocculating and clarification medium with solid aggregating particlesto form larger aggregates which do not deform under conditions of use infiltering or gravity separating them from the waste water. The combinedclarification flocculating medium comprises a mixture of solidaggregation or filter particles, and a dry flocculating agent effectiveto flocculate the solid particles in the waste water and aggregate themwith the aggregation or filter particles to form larger or heavierflocculated aggregates effective to gravity separate or filter from thewaste water. The flocculating agent (coagulant/flocculent) can benatural or synthetic, cationic, anionic, or nonionic, and can have anydesired molecular weight. Examples of natural coagulants used in thetechnology are natural alums, iron sulfates, ferric chloride, calciumchloride, and swelling clays. Examples of synthetic flocculents arepolyacrylamides, polyamines, and others. The flocculent component rangesfrom 0.1 percent to 85 percent. The natural products tend to work bestat 25 percent to 80 percent by weight of the total blend, and syntheticproducts work best at 0.1 percent to 5 percent by weight of the totalblend.

The aggregation particles can be any solid particles which will formaggregates with the solid particles in waste waters by flocculation.

The filter aid particles can be any particles which effectively filtersolids from liquids. Filter aid vendors offer their products in gradeswhich vary in particle size distribution which match proper grade(particle size) for filtration. Preferably, silicious particles orcombustible particles or a combination thereof are utilized. Forexample, silicious particles including biogenetic silica, such as ricehull ash, or diatomaceous earth or perlite or mixtures thereof can beutilized. Combustible particles, such as rubber, coal, or petroleum cokeparticles can be used preferably in a size range of about 5 mesh toabout 325 mesh. The combustible particles can be used alone or mixedwith up to about 70 percent by weight, preferably about 20 percent toabout 70 percent by weight, of silicious particles of the clarificationmedium.

In utilizing biogenetic silica, plants having a highly porous silicastructure are burned which contain a minimum of 15 percent silica byweight and preferably 20 percent or more. There are a limited number ofplants that contain these high quantities of silica. These are thestalks and hulls of rice, equisetum (horsetail weeds), certain bambooand palm leaves, particularly polymera, pollen, and the like, all ofwhich when burned leave a porous ash that is highly desirable as afiltration aid or medium.

The presently preferred biogenetic silica is rice hull ash. Rice hullsare high in silica content containing about 18 to 20 percent by weightwith the ash having a porous skeletal silica structure havingapproximately 75 to 80 percent open or void spaces by volume. For adescription of the commercial burning of rice hulls to provide rice hullash, its physical and chemical properties, reference is made to theforegoing patents and applications set forth in the "Background of theInvention."

The combustible particles preferably are rubber particles which can be awaste material, such as what is referred to as "buff rubber" or "crumbrubber." This is obtained by grinding of tire carcasses to provide aflat tire surface for a retread and grinding of new tires to finishthem. Also, old tires can be utilized in which the metal and cores areremoved, such as by cryogenic processes, which are utilized to separateout the metals such as by magnet from the cord.

The rubber component of the mixture may require treatment with a wettingagent in order to counteract hydrophobic characteristics which arefrequently found. The wetting agent prevents the rubber component fromseparating in the filtration stream thereby becoming ineffective,useless, and in fact a problem. Many low cost and widely known wettingagents such as industrial soaps and detergents are effective in a widerange of dosages from as little as 1 percent to as high as 10 percent byweight and higher. Preferably, the rubber particles should have a meshsize ranging from about 5 to 325 mesh. Advantageously, the addition of awetting agent addition imposes a negligible cost to the product and hasno deleterious effect on the filtration properties. The wetting agent isunnecessary in other than water based liquids and can be excluded, ifnecessary or desired.

As previously mentioned, current governmental recycling regulationsrequire the Btu content of the resulting filter cake to be at least 5000Btu's per pound of cake. At the present time, most recylers insist on atleast 6000 Btu's per pound of filter cake. The incineration isaccomplished by using the filter cake as a fuel in cement or lime kilns,industrial furnaces, and the like.

Advantageously filter presses are available currently on the openmarket, such as from Hoesch Industries, Inc., JWI, Inc., Netzsch, Inc.,Eimco, Inc., and Shriver, Inc., which can be used in the filteringaspects of the present invention.

The following examples demonstrate the advantages of a blended or mixedflocculating and clarifying medium combined into a single product andwhich performs better than separate use of the components and whichsolves a number of other problems associated with handling polymerflocculants.

EXAMPLE 1

This example demonstrates a key performance advantage of theflocculating clarifying medium's emulsion breaking capabilities.Emulsion breaking is a common task for polymers, and the degree ofsuccess can easily be measured with common turbidity equipment. For thistest a standard emulsion of 0.1 percent solution with latex paint(Glidden HD 6180) in water was tested. The emulsion was lightly tintedso that its quality could be quantified by a turbidimeter (Hach 2100P).A weighed quantity of test sample was stirred in a volume of thestandard emulsion, typically 500 ml, at 200 rpm for 5 minute intervals.At the end of each interval, the stirring was stopped for one minute toallow for a settling period. Then a small portion of the supernate wasremoved from a point one inch down from the top of the liquid level. Theturbidity of the removed supernate was measured and recorded. Lowturbidity values indicate clear liquid. The test was conductedsimultaneously on a number of doses. The following Table 1 illustratesthe results of a full series of tests.

                  TABLE 1                                                         ______________________________________                                        Rice Hull Ash + 0.2 wt % Polyacrylamide                                       (Stockhausen 851BC)                                                           Turbidity vs. Time for Various Doses                                          (Turbidity in Nephelometric Turbidity Units (NTU))                                      Sample Dose in Grams per Liter                                      Time, Min   4      6           8    10                                        ______________________________________                                        0-5         35.4   35.8        34.7 30.22                                      5-10       11.6   12.8        8.44 11.0                                      10-15       5.39   6.31        3.34 2.3                                       15-20       3.34   3.63        2.54 0.87                                      20-25       1.62   0.91        0.28 0.36                                      ______________________________________                                    

It is noted that for each dose the turbidity improved with longer time,and for each time the turbidity improved with increasing dose. Theturbidity of the untreated standard emulsion was determined by the useof a flocculation type stirrer (slow paddle variable speed stirrer withfour stir positions which is sometimes referred to as a gang mixer) andwas about 180 NTU.

EXAMPLE 2

This example is the same as Example 1 but was performed with rice hullash alone and no polymer treatment. The table below summarizes thefindings.

                  TABLE 2                                                         ______________________________________                                        Rice Hull Ash                                                                 Turbidity vs. Time for Various Doses                                          (Turbidity in Nephelometric Turbidity Units (NTU))                                      Sample Dose in Grams per Liter                                      Time, Min   4      6           8    10                                        ______________________________________                                        0-5         296    427         656  917                                        5-10       289    431         656  930                                       10-15       305    421         641  922                                       15-20       300    428         648  926                                       20-25       308    436         666  936                                       ______________________________________                                    

From the data in Table 2, the rice hull ash had almost no effect on theclarity of the standard emulsion.

EXAMPLE 3

This test was performed to determine the performance of the flocculentalone. Table 3 summarizes the results of this test.

                  TABLE 3                                                         ______________________________________                                        Polyacrylamide (Stockhausen 851BC) Only                                       Turbidity vs. Time for Various Doses                                          (Turbidity in Nephelometric Turbidity Units (NTU))                                      Sample Dose in Grams per Liter                                      Time, Min   .008   .012        .016 .020                                      ______________________________________                                        0-5         42.5   40.4        37.2 39.8                                       5-10       29.8   22.2        20.0 22.0                                      10-15       19.6   19.2        17.7 18.5                                      15-20       17.2   19.8        18.2 19.5                                      20-25       14.8   19.5        19.2 18.2                                      ______________________________________                                    

The data set forth in Table 3 is quite irratic. The inconsistentperformance data is most likely a result of the flocculant's difficultyat developing any clarity in a very low solids' environment. The datafurther demonstrates that this particular flocculant would be a poorchoice to break the emulsion in the water.

EXAMPLE 4

In this example a number of other flocculants, natural and syntheticwhich vary both in charge and magnitude, were tested. The naturalflocculants included natural alums, iron sulfates, ferris chloride,calcium chloride, and swelling or bentonitic clays. The syntheticflocculants included polyacrylamide and polyamine. While the resultingdetailed data were different, the results were similar. The combinedrice hull ash and flocculent achieved better clarity than either productalone. Thus, this combination has tremendous application in a largenumber of waste water applications where clarity by flocculation andsettling is a goal.

EXAMPLE 5

In this example two tests were performed to determine if there was anyperformance advantage from simultaneous addition of rice hull ash andthe flocculent over sequential addition protocols. In the first test a0.012 gram per liter dose of flocculent was added to 500 ml of standardemulsion which already contained a 5.988 gram per liter dose of ricehull ash. This ratio of flocculent to rice hull ash blend was equivalentto the 0.2 percent concentration set forth in Table 1. The example wasmixed, sampled at 5 minute intervals, and the results are set forth inthe following Table 4.

                  TABLE 4                                                         ______________________________________                                        Sample: Rice Hull Ash Added First                                             Turbidity vs. Time for Various Doses                                          (Turbidity in Nephelometric Turbidity Units (NTU))                                       Aggregate Dose in Grams per Liter                                  Time, Min  6                                                                  ______________________________________                                        0-5        41.6                                                                5-10      36.2                                                               10-15      31.7                                                               15-20      30.1                                                               20-25      31.9                                                               ______________________________________                                    

The data in Table 4 indicates a slight improvement in the clarity overthe course of this test but demonstrated that the 0.91 NTU at 20-25minute sample point for the combined product is far superior to the 31.9NTU achieved by the sequentially added sample at the same level.

EXAMPLE 6

To evaluate the effect of adding the flocculent first, the flocculentwas added to a standard emulsion at dosages equivalent to its componentdosage in the blended products (the same as in the flocculent onlytesting). The flocculent treated emulsions were stirred for 30 minutes,and turbidities were measured. Rice hull ash was then added at itscorresponding percentage, and the testing at 5 minute intervalscommenced. The results are set forth in the following Table 5.

                  TABLE 5                                                         ______________________________________                                        Polyacrylamide Added First                                                    Turbidity vs. Time for Various Doses                                          (Turbidity in Nephelometric Turbidity Units (NTU))                                       Sample Dose in Grams per Liter                                     Time, Min    4      6          8    10                                        ______________________________________                                         0-30        17.3   17.8       20.6 23.4                                      RHA ADDED                                                                      0-5         9.04   6.18       3.79 3.11                                       5-10        6.66   3.70       1.98 1.47                                      10-15        5.26   2.39       1.14 0.93                                      15-20        4.52   1.94       0.88 0.60                                      20-25        3.94   1.87       0.63 0.46                                      ______________________________________                                    

The turbidities for the dosages of the combined products at the 20-25minute cut were 1.62, 0.91, 0.28, 0.35 NTU, respectively, which arenoticeably better than the above turbidities.

Thus, on the clarity and settling phenomena it is quite clear that theaddition of the combined rice hull ash and polyacrylamide is better thaneither one alone or sequentially added. This is also the case with theother flocculants and aggregating particles set forth in Example 4.Thus, a single product, that is a combination of flocculating andaggregating particles, is a considerable improvement over either onealone.

EXAMPLE 7

The filtration performance of the blended product of Example 1 wasdemonstrated using the samples from the above flocculation test andflowing them into a convention laboratory pressure filter (Cuno Tri-47Model #70015-03A). The untreated samples filtered with a flux of about0.7 gallons per minute per square foot (gpm/sf), but the clarity waspoor at an 162 NTU. The fluxes of the combination of rice hull ash andflocculation agent (polyacrylamide) for the various doses are reportedin the following Table 6.

                  TABLE 6                                                         ______________________________________                                        Rice Hull Ash + 0.2 Wt % Polyacrylamide                                       (Stockhausen 851BC)                                                           Pressure Filtration Flow Test of Samples from Flocculation Test                          Sample Dose in Grams per Liter                                                4    6          8      10                                          ______________________________________                                        Flux, gpm/sf 5.5    7.3        6.6  2.8                                       Filtrate Clarity                                                                           1.69   0.39       0.26 0.16                                      NTU                                                                           ______________________________________                                    

The data in Table 6 is surprising. The fluxes are far higher thanexpected. It is considered extraordinary when the flux for thisfiltration apparatus reaches 2 or 2.5 gpm/sf. The flux for these testswas higher than the flux for water with no contamination.

The data in the above Table 6 indicates that the flux value peaks atabout 7.3 gpm/sf and then falls off with increasing dosage. This isconsistent with filtration theory in that as filter cake thicknessincreases, such is the case with increasing doses, because thefiltration area is constant for all increasing doses, because thefiltration area is constant for all dosages, the flow rate throughsolids decreases at a rate proportioned to the increase in filter cakethickness. The thicker the cake the slower the rate. Further, as filtercake thickness increases, clarity improves. The thicker the filter cakethe longer the flow path and the greater the opportunity for solids tobe captured. The clarity improves with dosage. While there was adegradation of flux in the 10 gram per liter over dose condition,filtration still proceeded at commercial rates. This is important andsignificant in industrial application. With a standard flocculationtreatment an overdose situation will interrupt operation. Equipmentbecomes so clogged with excess flocculent that a shut down is needed toclean up the equipment. With the rice hull ash self flocculating filteraid filter flux may degrade slightly but not to any serious degree.Further, the operation will not need to be shut down to clean up theequipment from the overdose.

EXAMPLE 8

In this example, rice hull ash samples were subjected to filtrationtests. The results are set forth in the following Table 7.

                  TABLE 7                                                         ______________________________________                                        Rice Hull Ash + No Flocculant                                                 Flow Test Samples from Flocculation Test                                                 Sample Dose in Grams per Liter                                                4    6          8      10                                          ______________________________________                                        Flux, gpm/sf 0.25   0.13       0.32 0.15                                      Filtrate clarity                                                                           6.74   4.19       5.66 2.57                                      NTU                                                                           ______________________________________                                    

From Table 7 it is seen that rice hull ash achieves extremely smallfluxes, and the filtrate clarities are generally one order of magnitudeworse than those for the combined rice hull ash-flocculent blend. Thisis consistent because it is clear from the data from thestirring/settling/clarity tests that the emulsion was not broken as itwas for the combined product.

EXAMPLE 9

In this example the waste water was filtered with polyacrylamide polymeralone. There was no filter flux data as the flocculated waste water onlyflowed a few milliliters before stopping completely. This is notunusual. Aggregates created only from flocculant treatment are extremelydeformable and difficult to filter.

EXAMPLE 10

One commercial application for gravity separation or filtration is tobreak emulsions and colloids. The large surface area of silicaseparation of filter aids (9-18 square meters per gram depending ongeneric type and grain grade) provides sites for coalescence of oil,water emulsions, and the fine porous systems filter out the solids ofcolloidal systems.

In this example a latex paint waste water required treatment to removethe spent latex. With the latex in it, waste water was a combination ofemulsion and colloidal problem. The waste latex contributes suspendedsolids (TSS), chemical oxygen demand (COD) and biological oxygen demand(BOD) in excess of regulatory limits so must be removed.

The treatment in this example was to remove the latex in a costeffective manner. Removal of the latex was quantified by the clarity ofthe filtrate (EPA approved 2100p turbidimeter which reports innephelometric turbidity units (NTU)). The economics in this example arequantified by low chemical additions and high filter flow rates whichequate to smaller capital equipment.

This example has the added benefit of demonstrating the performance ofboth natural and synthetic flocculating in self flocculation technology.The turbidity of the untreated water feed was 892 NTU. The results ofthis example are illustrated in the following Table 8.

                  TABLE 8                                                         ______________________________________                                                     Dose   Flux    Filtrate Clarity                                               gm/L   gpm/sf  NTU                                               ______________________________________                                        Rice Hull Ash  18       0.06    26.6                                          50% RHA and 50%                                                                              18       .26     20.1                                          Bentonite Clay                                                                99% RHA and 1%  8       2.91    0.97                                          Cationic Polyacrylamide                                                       (Drew Chemicals                                                               Drew Floc 41)                                                                 ______________________________________                                    

EXAMPLE 11

In this example a blend of 47.5 wt. percent rice hull ash, 47.5 wt.percent--20 mesh crumb rubber, and 5 percent wetting agent was tested.Blends of rice hull ash and rubber particles are commonly used in oilysludge treatment. This blend had a flux and a caloric content which weresuperior to any of the other products tested. A diatomaceous earthproduct, Eagle Pitcher FW 60, is a popular product for this service andis a pure mineral filter aid which has no native caloric value. As aconsequence, the caloric value of the resulting filter cake was low at2110 btu per pound of filter cake. Data from the testing of rice hullash was also presented. It was superior to the diatomaceous earthproduct in both flux and heating values but still did not develop thecaloric content necessary for low cost incineration under federal BIFregulations. Also, there are two sets of data from testing the low ashcombined with charge flocculation agents such as polymers. The dataincludes adding the flocculant separately. The following data in Table 9demonstrates the performance advantage of the flocculant blended versionboth in flux and calorie content compared to adding the flocculantseparately.

                  TABLE 9                                                         ______________________________________                                                        Dose  Flux    Caloric Value                                                   gm/L  gpm/sf  Btu/lb                                          ______________________________________                                        NO POLYMER                                                                    Diatomaceous Earth                                                                              25      .0154   2110                                        Eagle Pitcher FW 60                                                           Rice Hull Ash     25      0.056   2350                                        POLYMER ADDED SEPARATELY                                                      47.5% Wt. Rice Hull Ash,                                                                        25      0.180   6190                                        47.5% Wt. - 20 crumb rubber,                                                  5% wetting agent                                                              5.0% Wt Synthetic 1.8                                                         Polymer (TTA 805)                                                             POLYMER BLENDED                                                               47.5% Wt Rice Hull                                                                              25      0.190   6210                                        Ash + 47.5% Wt. - 20 crumb                                                    rubber                                                                        0.4% Wt. Synthetic                                                            Polymer  Stockhausen                                                          644BC!                                                                        ______________________________________                                    

From the foregoing data in Table 9 the two ash samples including crumbrubber both had a filter cake whose caloric value was in excess of 6000btu per pound so that they can be disposed of in the low cost andfederally regulated BIF program.

EXAMPLE 12

In this example a rice hull ash based metal sequestering filter aid wastested which is most commonly consumed in the treatment of metals ladenwaste waters. Flocculation or polymer treatment is often required as anadjunct treatment to help defeat problems created by emulsions and/orfine particle precipitates such as organic or inorganic sulfideprecipitation. In this example, the waste water was from a manufacturerof chemicals for surface heat treating. The waste water was acombination of reactor wash down and floor waste. It included hydroxideand sulfide precipitated metals as well as emulsion forming surfactants.The results of this test are set forth in Table 10.

                  TABLE 10                                                        ______________________________________                                                     Flux   Filtrate Clarity                                                       gpm/sf NTU        Pass TCLP                                      ______________________________________                                        75 Wt % Rice Hull Ash,                                                                       0.245    1.68       Yes                                        25 Wt % Synthetic and                                                         Natural pozyolans                                                             Polyacrylamide Polymer Only                                                                  0.096    1.97       No                                         (Stockhausen 655 BC)                                                          74.7 Wt % Rice Hull Ash,                                                                     0.862    0.39       Yes                                        24.9 Wt % synthetic and                                                       Natural Pozyolans,                                                            0.4 Wt % Synthetic Polymer                                                    (Stockhausen 655 BC)                                                          ______________________________________                                    

From the data in Table 10 the blended version of rice hull ash andflocculent was superior in all performance categories. The data for ricehull ash indicates a usable flux, but the 1.68 NTU filtrate clarityindicates that the emulsion is not completely treated. The flocculent orpolymer only is unsatisfactory in all performance areas. The flux isunacceptably low, clarity is poor, and the filter cake fails to federalleaching tests. The flocculent or polymer blended rice hull ash isclearly superior in all performance categories. The foregoing is true ofall flocculants and aggregates.

The present invention therefore is well suited and adapted to attain theobjects and ends and has the advantages and features mentioned as wellas others inherent therein.

While presently preferred embodiments of the invention have been givenfor the purpose of disclosure, changes can be made therein which arewithin the spirit of the invention as defined by the scope of theappended claims.

What is claimed is:
 1. A combined flocculating and clarifying medium forflocculating and removing solid particles from waste water comprising,ablended mixture of a dry flocculating agent and solid aggregatingparticles selected from the group consisting of cationic, anionic, andnonionic agents effective to flocculate the solid particles in the wastewater into flocculated solid aggregates with the aggregating particlesof a size and weight effective to clarify them from the waste water bygravity separation or filtration.
 2. The combined flocculating andclarifying medium of claim 1 where,the flocculating agent is present inan amount from about 0.1 percent to about 85 percent by weight.
 3. Thecombined flocculating and clarifying medium of claim 1 where,theflocculating agent is a natural substance.
 4. The combined flocculatingand clarifying medium of claim 1 where,the flocculating agent is anatural substance and is present in an amount of from about 25 percentto about 85 percent by weight of the blended mixture.
 5. The combinedflocculating and clarifying medium of claim 1 where,the flocculatingagent is a synthetic material.
 6. The combined flocculating andclarifying medium of claim 1 where,the flocculating agent is a syntheticmaterial and is present in an amount of from about 0.1 percent to about5 percent by weight of the blended mixture.
 7. The combined flocculatingand clarifying medium of claim 1 where,the solid aggregating particlesare silicious particles.
 8. The combined flocculating and clarifyingmedium of claim 1 where,the solid aggregating particles are biogeneticsilica.
 9. The combined flocculating and clarifying medium of claim 1where,the solid aggregating particles are silicious particles selectedfrom the group consisting of rice hull ash, diatamaceous earth, andperlite.
 10. The combined flocculating and clarifying medium of claim 1where,the solid aggregating particles comprise combustible particles andare present in an amount sufficient to provide at least 5000 Btu perpound of the blended mixture including the filtered flocculated solidparticles.
 11. The combined flocculating and clarifying medium of claim1 where,the solid aggregating particles are selected from the groupcomprising rubber, coal, petroleum coke, and mixtures thereof, particlesin a mesh size of from about 5 mesh to 325 mesh and have a Btu contentof at least 5000 Btu per pound of the blended mixture including theflocculated solid particles clarified.
 12. A composition of mattercomprising,a blended mixture of a dry flocculating agent and siliciousparticles effective to flocculate and aggregate solid particles in wastewaters effective to clarify them from waste water by gravity separation.13. The composition of matter of claim 12 where,the dry flocculatingagent is a natural material and is present in the blended mixture in therange of about 25 percent to about 80 percent by weight.
 14. Thecomposition of matter of claim 13 where,the silicious particles areselected from the group consisting of rice hull ash, diatomaceous earth,and perlite.
 15. The composition of matter of claim 12 where,the dryflocculating agent is a synthetic material and is present in the blendedmixture in the range of about 0.1 percent to about 5.0 percent byweight.
 16. The composition of matter of claim 15 where,the siliciousparticles are selected from the group consisting of rice hull ash,diatomaceous earth, and perlite.
 17. The composition of matter of claim12 where,the filtering particles have a Btu content of at least 5000 Btuper pound of the mixture including the flocculated solid aggregates. 18.The composition of matter of claim 12 where,the blended mixture includesa polyvalent metal ion, at least some of the silicious particlesdissolve in the waste water when having a pH of at least 12 to form asoluble silicate, the polyvalent metal ion being present in an amountsufficient to form a silicious cement with the soluble silicate and tochemically fix the flocculated solids in the silicious cement.
 19. Thecomposition of matter of claim 18 where,the silicious particles areselected from the group consisting of rice hull ash, diatomaceous earth,and perlite.